Fuel cell with proton exchange membrane bonded to acrylic plastic element

ABSTRACT

A proton exchange membrane fuel cell comprises a membrane formed from a fluorocarbon ionic polymer material capable of being bonded to an acrylic, preferably a polymethylmethacrylate polymer, and at least one desirably electrically conductive plate bonded to an area of a face of the membrane via an acrylic plastic material. The bond may be accomplished by positioning a layer of the acrylic plastic material between a surface of the plate and an area of a face of the membrane. Alternatively, the plate may be constructed of the acrylic plastic material and a surface thereof may be bonded directly to an area of a face of the membrane.

CROSS REFERENCE TO RELATED APPLICATION

None

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention of the present application relates to fuel cells and tomethodology for preparing the same. In particular, the invention relatesto proton exchange membrane (PEM) fuel cells and to the components andmethodology for securing gas reservoir and/or current collector platesto PEMs.

2. The Prior Art Background

PEM fuel cells generally may be constructed in the form of assemblieswhich include a membrane with two electrodes, one on each side of themembrane. Such an assembly is generally referred to as a membrane andelectrode assembly (MEA). A respective plate is placed in contact witheach electrode. Typically each such plate has channels or compartmentstherein which act as fuel and oxidant reservoirs for the electrodes.When such plates are electrically conductive they may also act aselectrical current collectors for the fuel cell.

In the past, and among other things, gaskets have often been utilized toseal the fuel and oxidant compartments from the ambient surroundings.Such gaskets are generally situated at the peripheral sides of theexposed membrane as shown in FIGS. 1 a and 1 b which schematicallydepict a prior art PEM fuel cell. With reference to FIGS. 1 a and 1 b,the former depicts the fuel cell in an exploded condition while thelatter depicts the assembled fuel cell. As shown in FIGS. 1 a and 1 b,the fuel cell 20 includes a fuel plate 22 having a fuel reservoircompartment or channels 24 and an oxidant plate 26 with oxidantreservoir compartment or channels 28. An MEA 30 is positioned betweenthe plates 22, 26 and has its outer edges 30 a, 30 b compressed betweengaskets 32 a, 32 b, 32 c, 32 d using nut and bolt assemblies 34 a, 34 b.

Other prior art fuel cells are illustrated in U.S. Pat. No. 6,641,862,U.S. Pat. No. 6,740,445 and U.S. Pat. No. 6,733,914, the entireties ofthe disclosures of which are incorporated herein by this specificreference thereto.

It is necessary to insure a secure and appropriate seal around the edgesof the membrane and so either compression must be applied via the platesor some sort of bonding material must be applied between the gasket andthe membrane and between the gasket and the adjacent surfaces of theplates. Adhesion without the need for compressive means such as the nutand bolt assemblies 34 a, 34 b of FIG. 1 b is desirable; however,finding a suitable bonding material for this application has been a verychallenging task because the membranes used in such a fuel cell systemundergo physical changes (i.e., swelling and shrinkage) as the same gainand lose water during operation.

SUMMARY OF THE INVENTION

An important and essential object of the present invention, therefore,is to provide a PEM fuel cell wherein a secure and appropriate seal isprovided between the MEA and the fuel and/or oxidant plates associatedtherewith. To this end, and in accordance with the concepts andprinciples of one very important aspect of the invention, a novel PEMfuel cell is provided which comprises a membrane formed from a materialcapable of being bonded to an acrylic plastic and at least one acrylicplastic element having a surface bonded to an area of a face of themembrane.

In further accordance with the concepts and principles of the invention,the membrane may desirably be formed from a material that is capable ofbeing thermally and compressively bonded to an acrylic plastic,preferably a fluorocarbon ionic polymer, ideally Nafion®. In furtheraccordance with the concepts and principles of the invention, theacrylic plastic material may desirably comprise a polymethylmethacrylatepolymer.

In still further accordance with the concepts and principles of theinvention, the PEM fuel cells may include a fuel or oxidant plate thatis bonded to a proton exchange fuel cell membrane utilizing a layer ofacrylic plastic disposed between the membrane and the plate.Alternatively, the plate itself may be formed from the acrylic plasticand the same may be bonded directly to the membrane.

Another important and essential object of the present invention is toprovide a method for preparing a PEM fuel cell comprising supplying amembrane formed from a material capable of being bonded to an acrylicplastic and affixing a plate, which is either a fuel plate or an oxidantplate, to said membrane using an acrylic plastic substance. Inaccordance with this aspect of the invention, the acrylic substance maybe in the form of a layer of the same disposed between the membrane anda fuel or oxidant plate. In the alternative, the plate itself may beformed from an acrylic plastic substance and the same may be bondeddirectly to the membrane. Desirably, the membrane may be a fluorocarbonionic polymer, preferably Nafion. Ideally the acrylic plastic maycomprise a polymethylmethacrylate polymer.

In one preferred form of the invention, the membrane may be thermallybonded to a face of the acrylic plastic substance using heat andcompression.

Desirably, in accordance with the invention, the plates may beelectrically conductive whereby to act as electrical current collectorsfor the fuel cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic, exploded, cross-sectional depictionillustrating a prior art PEM fuel cell;

FIG. 1 b is a schematic, cross-sectional depiction illustrating the PEMfuel cell of FIG. 1 a after assembly of the separate components;

FIG. 2 a is a schematic, exploded, cross-sectional depictionillustrating an embodiment of a PEM fuel cell which includes theprinciples and concepts of the invention;

FIG. 2 b is a schematic, cross-sectional depiction illustrating the PEMfuel cell of FIG. 2 a after assembly of the separate components;

FIG. 3 is a schematic, cross-sectional depiction illustrating a secondembodiment of a PEM fuel cell which embodies the principles and conceptsof the invention; and

FIG. 4 is a schematic, cross-sectional depiction illustrating a thirdembodiment of a PEM fuel cell which embodies the principles and conceptsof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A PEM fuel cell 50 which embodies the principles and concepts of theinvention is illustrated in FIGS. 2 a and 2 b where it can be seen thatthe same may desirably include a fuel plate 52 having a fuel compartmentor channels 54 and a oxidant plate 56 having an oxidant compartment orchannels 58. In this regard, the plates 52, 56 of FIGS. 2 a, 2 b aresimilar to the plates 22, 26 of the prior art cell 20. The fuel cell 50also includes an MEA 60 which again is similar to the MEA 30 of FIGS. 1a, 1 b. However, and in accordance with the invention, the fuel cell 50which embodies the invention may include acrylic layers or elements 55a, 55 b, 55 c, 55 d disposed respectively between the edges 62 a, 62 bof the membrane 62 of MEA 60 and the adjacent edges 52 a, 52 b, 56 a, 56b of the plates 52, 56, as shown. In accordance with the invention, theMEA 60 may be a conventional product such as the MEAs manufactured byIon Power, Inc. In this regard, the MEA 60 may preferably include acatalyst layer 63 on each side thereof as shown schematically in FIGS. 2a, 2 b. Desirably, the plates 52, 56 may be electrically conductivewhereby to act as electrical current collectors for the fuel cell 50.

In further accordance with the principles and concepts of the inventionwhich is the subject of the present application, it has been discoveredthat the membrane 62 of the MEA 60 may desirably be formed of afluorocarbon ionic polymer, preferably a perfluorosulfonic acid polymer,such as Nafion® (Nafion® is a registered trademark of E.I. du Pont deNemours Company), or the like. In this regard, and in still furtheraccordance with the principles and concepts of the invention, it hasbeen discovered that fluorocarbon ionic polymer materials may bethermally bonded directly to an acrylic plastic, preferablypolymethylmethacrylate, surface using heat and compression. Sinceacrylic plastics themselves are readily bondable to many surfaces by anyone or more of a multitude of available adhesives, this approach allowsareas of a face of a membrane such as the membrane 62 of the MEA 60 ofthe PEM fuel cell 50 to be bonded to a surface of the fuel plate 52 oroxidant plate 56, or both, thereby providing an excellent and veryfacile process for sealing the MEA 60 and the fuel and oxidantcompartments 54, 58 from the surrounding ambient. This reduces andperhaps completely eliminates the need for the use of compressivedevices such as the nut and bolt assemblies 34 a, 34 b of FIG. 1 b forapplying compression to seal the fuel cell assembly. FIGS. 2 a, 2 b thusshow an embodiment of the invention in which acrylic films 55 a, 55 b,55 c, 55 d bonded to faces of the membrane 62 at edges 62 a, 62 bthereof are glued to corresponding surfaces 52 a, 52 b, 56 a, 56 b ofthe fuel and oxidant plates 52, 56 and the fuel and oxidant are providedto the cell 50 through channels 54, 58 of the fuel and oxidant plates52, 56.

Another embodiment of a PEM fuel cell which embodies and incorporatesthe concepts and principles of the invention is illustrated in FIG. 3where the cell is identified by the reference numeral 250. In FIG. 3 itcan be seen that fuel may be provided to cell 250 through a fuel plate252 and the membrane 262 of the MEA 260 is bonded to acrylic elements255 a, 255 c which in turn are glued to the fuel plate 252. The cell 250may preferably be provided with an integrated current collector 275 onthe oxidant side, and the oxidant, air as an example, may then beobtained directly from ambient as is indicated schematically in FIG. 3.

FIG. 4 illustrates a cell 350 which is similar to the cell 250 of FIG.3, except in this case the entire fuel plate 352 may desirably be formedfrom an acrylic plastic. The corresponding surfaces at the edges ofacrylic plastic fuel plate 352 may then be thermally bonded directly toareas of the face of the membrane 362 of MEA 360 at the edges 362 a, 362b thereof. With this construction, acrylic elements such as the acrylicelements 255 a, 255 c of FIG. 3 are not needed and may be eliminatedcompletely. Also, in this embodiment the cell 350 may desirably includean integrated current collector 377 on the fuel side as shown.

With further reference to FIGS. 2 a, 2 b, and as would be readilyapparent to one of ordinary skill in the PEM fuel cell art, either thefuel plate 52, or the oxidant plate 56, or both, could be made entirelyof an acrylic plastic, like the plate 352 of FIG. 4, and thermallybonded directly to the edges 62 a, 62 b of the membrane 62. In each ofthese cases, the corresponding acrylic layers may then be eliminatedthereby avoiding the need for the intermediate step of attaching acrylicelements to the corresponding plates. In such a case it would bedesirable to include an integrated current collector, such as thecollector 377 of FIG. 4, on each side where the plate is made entirelyof plastic since acrylic plastics are not generally considered to beelectrically conductive materials.

In the foregoing description, during the assembly of a fuel cell whichincludes a layer or film of acrylic plastic it has sometimes beenindicated that the sequence of assembly might be to first bond theacrylic layer or element to the edges of the membrane and then to attachthe respective plate to the acrylic layer. However, and as would bereadily apparent to one of ordinary skill in the art, it is perhapsequally valuable to sometimes reverse this procedure and first attachthe acrylic layer to the plate and then bond the acrylic layer to themembrane.

1. A proton exchange membrane fuel cell comprising a membrane formedfrom a material capable of being bonded to an acrylic plastic and atleast one acrylic plastic element having a surface bonded to an area ofa face of the membrane.
 2. A proton exchange membrane fuel cell as setforth in claim 1, wherein said material is a fluorocarbon ionic polymer.3. A proton exchange membrane fuel cell as set forth in claim 2, whereinsaid polymer comprises Nafion®.
 4. A proton exchange membrane fuel cellas set forth in claim 1, wherein said acrylic plastic comprises apolymethylmethacrylate polymer.
 5. A proton exchange membrane fuel cellas set forth in claim 1, wherein said material is capable of beingthermally bonded to an acrylic plastic using heat and compression andsaid surface of said element is thermally bonded to said face.
 6. Aproton exchange membrane fuel cell as set forth in claim 2, wherein saidacrylic plastic comprises a polymethylmethacrylate polymer and saidsurface of said element is thermally bonded to said face.
 7. A protonexchange membrane fuel cell as set forth in claim 3, wherein saidacrylic plastic comprises a polymethylmethacrylate polymer and saidsurface of said element is thermally bonded to said face.
 8. A protonexchange membrane fuel cell as set forth in claim 1, wherein saidelement comprises a layer of said acrylic plastic and said fuel cellincludes a fuel or oxidant plate attached to an opposing surface of saidlayer.
 9. A proton exchange membrane fuel cell as set forth in claim 1,wherein said element comprises a fuel or oxidant plate.
 10. A protonexchange membrane fuel cell as set forth in claim 8, wherein said plateis electrically conductive.
 11. A proton exchange membrane fuel cell asset forth in claim 9, comprising an integrated current collectorcooperating with said membrane.
 12. A proton exchange membrane fuel cellas set forth in claim 1 comprising at least two of said acrylic plasticelements, a first of said elements having a surface bonded to an area ofa first face of the membrane and a second of said elements having asurface bonded to an area of a second opposing face of the membrane. 13.A proton exchange membrane fuel cell as set forth in claim 12, whereinat least one of the elements is a layer of said acrylic plastic and saidfuel cell includes a fuel or oxidant plate attached to an opposingsurface of said layer.
 14. A proton exchange membrane fuel cell as setforth in claim 12, wherein each of the elements is a layer of saidacrylic plastic and said fuel cell includes a fuel plate attached to anopposing surface of the first layer and a oxidant plate attached to anopposing surface of the second layer.
 15. A proton exchange membranefuel cell as set forth in claim 12, wherein the first element comprisesa fuel plate and the second element comprises a oxidant plate.
 16. Aproton exchange membrane fuel cell as set forth in claim 9 comprising atleast two of said elements, a first of said elements having a surfacebonded to an area of a first face of the membrane and a second of saidelements having a surface bonded to an area of a second opposing face ofthe membrane.
 17. A proton exchange membrane fuel cell as set forth inclaim 16, wherein at least one of the elements is a layer of saidpolymethylmethacrylate polymer and said fuel cell includes a fuel oroxidant plate attached to an opposing surface of said layer.
 18. Aproton exchange membrane fuel cell as set forth in claim 16, whereineach of the elements is a layer of said polymethylmethacrylate polymerand said fuel cell includes a fuel plate attached to an opposing surfaceof the first layer and a oxidant plate attached to an opposing surfaceof the second layer.
 19. A proton exchange membrane fuel cell as setforth in claim 16, wherein the first element comprises a fuel plate andthe second element comprises a oxidant plate.
 20. A method for preparinga proton exchange membrane fuel cell comprising supplying a membraneformed from a material capable of being bonded to an acrylic plastic andaffixing a plate which is either a fuel plate or a oxidant plate to saidmembrane using an acrylic plastic substance.
 21. A method as set forthin claim 20, wherein said plate is formed from said substance.
 22. Amethod as set forth in claim 20, wherein said plate is affixed to saidmembrane using a layer of said substance disposed therebetween.
 23. Amethod as set forth in claim 20, wherein said material is a fluorocarbonionic polymer.
 24. A method as set forth in claim 23, wherein saidpolymer comprises Nafion®.
 25. A method as set forth in claim 20,wherein said acrylic plastic comprises a polymethylmethacrylate polymer.26. A method as set forth in claim 20, wherein said material is capableof being thermally bonded to an acrylic plastic using heat andcompression and said surface of said element is thermally bonded to saidface.
 27. A method as set forth in claim 20, wherein said plate iselectrically conductive.
 28. A method as set forth in claim 23, whereinsaid acrylic plastic comprises a polymethylmethacrylate polymer.
 29. Aproton exchange membrane fuel cell as set forth in claim 14, whereinsaid plates are electrically conductive.
 30. A proton exchange membranefuel cell as set forth in claim 15, comprising a respective integratedcurrent collector for each side of the membrane.